At a base station of cell phones and the like, a coaxial connector is used to transmit a high-frequency signal. A plug provided at the end of a coaxial cable and a receptacle which mates with the plug are both example of the coaxial connector.
The plug and the receptacle each include a center conductor and an external conductor surrounding the center conductor. When the plug and the receptacle mate with each other, the center conductors are connected to each other and the external conductors are connected to each other.
Note that techniques related to the present application are also described in the following documents: Japanese Laid-open Utility Model Publication No. 63-504, Japanese Laid-open Patent Publication No. 2013-84498, Japanese Laid-open Patent Publication No. 05-41259 and Japanese Laid-open Patent Publication No. 2009-52913.